Atlanta gave the Mavericks a second-round pick in the 2007 NBA draft in exchange for Johnson, who played for Atlanta from 1998-2000 and again in 2000-01.
Johnson is going from a team with the best record in the NBA Western Conference to one 5 1/2 games out of eighth place -- the final playoff slot -- in the Eastern Conference.
"We're happy to be able to bring Anthony Johnson back to Atlanta," said Hawks General Manager Billy Knight in a release. "He provides us with another veteran presence and brings a great deal of regular season and postseason experience to our club."
Johnson, 32, appeared in 40 games for Dallas this season and averaged 3.8 points and two assists per game. He has appeared in 586 NBA regular-season games, averaging 5.6 points and 2.8 assists. Johnson also played for Sacramento, Orlando, Cleveland, New Jersey, Indiana, Atlanta and Dallas.